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Posted to commits@cassandra.apache.org by "Mck SembWever (JIRA)" <ji...@apache.org> on 2011/08/30 23:23:13 UTC
[jira] [Issue Comment Edited] (CASSANDRA-2388)
ColumnFamilyRecordReader fails for a given split because a host is down,
even if records could reasonably be read from other replica.
[ https://issues.apache.org/jira/browse/CASSANDRA-2388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13094097#comment-13094097 ]
Mck SembWever edited comment on CASSANDRA-2388 at 8/30/11 9:22 PM:
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This approach isn't really working for me and was committed too quickly i believe.
bq. Although the documentation on inputSplit.getLocations() is a little thin as to whether this restricts which trackers it should run on or whether is just a preference
Tasks are still being evenly distributed around the ring regardless of what the ColumnFamilySplit.locations is.
The chance of a task actually working is RF/N. Therefore the chances of a blacklisted node are high. Worse is that the whole ring can quickly become blacklisted.
http://abel-perez.com/hadoop-task-assignment has an interesting section in it explaining how the task assignment is supposed to work (and that data locality is preferred but not a requirement). Could ColumnFamilySplit.locations be in the wrong format? (eg they should ip not hostname?).
was (Author: michaelsembwever):
This approach isn't really working for me and was committed too quickly i believe.
bq. Although the documentation on inputSplit.getLocations() is a little thin as to whether this restricts which trackers it should run on or whether is just a preference
Tasks are still being evenly distributed around the ring regardless of what the ColumnFamilySplit.locations is.
The chance of a task actually working is RF/N. Therefore the chances of a blacklisted node are high. Worse is that the whole ring can quickly become blacklisted.
> ColumnFamilyRecordReader fails for a given split because a host is down, even if records could reasonably be read from other replica.
> -------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-2388
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2388
> Project: Cassandra
> Issue Type: Bug
> Components: Hadoop
> Affects Versions: 0.6
> Reporter: Eldon Stegall
> Assignee: Mck SembWever
> Labels: hadoop, inputformat
> Fix For: 0.7.9, 0.8.5
>
> Attachments: 0002_On_TException_try_next_split.patch, CASSANDRA-2388-addition1.patch, CASSANDRA-2388-extended.patch, CASSANDRA-2388.patch, CASSANDRA-2388.patch, CASSANDRA-2388.patch, CASSANDRA-2388.patch
>
>
> ColumnFamilyRecordReader only tries the first location for a given split. We should try multiple locations for a given split.
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